Mechanical properties of forged low Ni and C-containing Co-Cr-Mo biomedical implant alloy

In order to examine the influence of variation in grain size and microstructure on mechanical properties of a low Ni and C-containing Co-29Cr-6Mo alloy for biomedical implant materials, the tensile properties and the dry friction wear characteristics of the wrought Co-29Cr-6Mo alloy without addition of Ni and C were investigated. The microstructure of as-forged alloys, consisting of fcc phase mixed with athermal hcp martensite, is found to become finer as the reduction during forging increases. The hot-forging processes for fabricating the fine microstructure with different grain sizes of 43, 11 and 3 pm has been successfully established under the condition that forging temperature of higher than 1273 K is strictly kept during forging. The tensile properties, such as the yield stress, the tensile stress and the elongation, are improved with decreasing the gram size and thereby increasing the volume fraction of the fcc phase in the microstructure. The dry wear resistance against the alumina ball is enhanced by decreasing the grain size.